Large databases are designed to manage vast volumes of data and therefore the speed in which queries may be performed on the database is important.
SQL (Standard Query Language) is a programming language that is used for managing data in relational database management systems (RDBMS).
User-Defined Functions (UDFs) were introduced in connection with large databases that include libraries of functions that can be defined by a user for operating on a database. UDFs are suited for analytic operations that are relatively difficult to perform in SQL, and that may be performed frequently enough that their performance is a concern.